Bandwidth Calculator
- Updated
- Formula shown
- Free, no sign-up
Results
5 GB at 100 Mbps takes 6 min 40 s
| Speed | Time |
|---|---|
| 10 Mbps | 1 h 6 min 40 s |
| 25 Mbps | 26 min 40 s |
| 50 Mbps | 13 min 20 s |
| 100 Mbps | 6 min 40 s |
| 300 Mbps | 2 min 13 s |
| 500 Mbps | 1 min 20 s |
| 1 Gbps | 40 s |
| 10 Gbps | 4 s |
Speeds are in bits per second and file sizes in bytes: 1 byte = 8 bits, so 100 Mbps moves at most 12.5 MB per second.
How to use the bandwidth calculator
- Choose a calculation: transfer time, speed needed, website bandwidth or unit conversion.
- Enter the file size and pick its unit carefully: MB and GB are decimal (10⁶ and 10⁹ bytes), MiB and GiB are binary (2²⁰ and 2³⁰ bytes).
- Enter the connection speed, usually in Mbps (megabits per second) as advertised by internet providers.
- Optionally add an overhead percentage for protocol headers and real-world slowdowns, then read the result and the table of common speeds.
Bandwidth formulas
speed needed (bit/s) = size (bytes) × 8 ÷ time (s) ÷ (1 − overhead ÷ 100)
monthly data = page views × page size × redundancy factor
The key step is the factor of 8. Internet speeds are sold in bits per second, while files are measured in bytes, and a byte is 8 bits. Prefixes matter too: network speeds always use decimal prefixes (1 Mbps = 1,000,000 bits per second), but file sizes may be decimal or binary, and a gibibyte is about 7.4% larger than a gigabyte. Overhead is the share of the line speed that doesn't carry your data. With TCP over IPv4 on Ethernet and full-size packets, 1,460 bytes of data travel in every 1,538 bytes on the wire, about 5.1% overhead, before any congestion or Wi-Fi losses.
Worked example
A 5 GB file on a 100 Mbps connection is 5 × 10⁹ × 8 = 40 billion bits; at 100 million bits per second that takes 400 seconds, or 6 min 40 s. With 5% overhead it takes 7 min 1 s. If the file is really 5 GiB (as many operating systems report sizes), it takes 7 min 9 s. Going the other way, moving 10 GB in 10 minutes needs at least 133 Mbps.
For a website with 100,000 page views a month and an average page weight of 2 MB, the monthly transfer is 200 GB. Spread over an average month that is 608 kbps; with a redundancy factor of 1.5 for busy periods, plan for 300 GB a month and about 913 kbps.
Download times at common speeds
| File size | 25 Mbps | 100 Mbps | 300 Mbps | 1 Gbps |
|---|---|---|---|---|
| 100 MB | 32 s | 8 s | 2.67 s | 800 ms |
| 1 GB | 5 min 20 s | 1 min 20 s | 26.7 s | 8 s |
| 5 GB | 26 min 40 s | 6 min 40 s | 2 min 13 s | 40 s |
| 25 GB | 2 h 13 min 20 s | 33 min 20 s | 11 min 7 s | 3 min 20 s |
| 100 GB | 8 h 53 min 20 s | 2 h 13 min 20 s | 44 min 27 s | 13 min 20 s |
These are best-case times at the full line speed with no overhead. Real downloads are usually slower.
Data-rate units
| 1 of this unit | In Mbps | In MB/s |
|---|---|---|
| kbps | 0.001 | 0.000125 |
| Mbps | 1 | 0.125 |
| Gbps | 1,000 | 125 |
| kB/s | 0.008 | 0.001 |
| MB/s | 8 | 1 |
| MiB/s | 8.388608 | 1.048576 |
| GB/s | 8,000 | 1,000 |
Why downloads are slower than the advertised speed
- Bits, not bytes. A "100 meg" connection is 100 megabits per second, at most 12.5 megabytes per second.
- Overhead and sharing. Protocol headers, Wi-Fi conditions, other devices on the network and busy times all take a share.
- The other end. A download can't go faster than the server sends it, and uploads are often much slower than downloads on home connections.
- Binary sizes. A file shown as 5 GB by your computer may be 5 GiB, about 5.37 billion bytes.
To convert storage units, use the conversion calculator. To plan network addresses, try the IP subnet calculator; for transfer times you can add to a schedule, the time duration calculator helps.
Frequently asked questions
How long does it take to download 5 GB at 100 Mbps?
About 6 minutes 40 seconds at the full line speed: 5 GB is 40 billion bits, and 40,000,000,000 ÷ 100,000,000 bits per second is 400 seconds. With 5% overhead it is about 7 minutes 1 second. Real downloads are often slower still.
How do I convert Mbps to MB/s?
Divide by 8, because a byte is 8 bits: 100 Mbps is 12.5 MB/s and 1 Gbps is 125 MB/s. In binary units, 100 Mbps is about 11.92 MiB/s. Lowercase b means bits and uppercase B means bytes.
What is the difference between GB and GiB for download times?
A GB is 1,000,000,000 bytes and a GiB is 1,073,741,824 bytes, about 7.4% more. At 100 Mbps, 5 GB takes 6 minutes 40 seconds while 5 GiB takes about 7 minutes 9 seconds. Internet speeds always use decimal prefixes.
What speed do I need to upload 10 GB in 10 minutes?
At least 133 Mbps: 10 GB is 80 billion bits, and 80,000,000,000 ÷ 600 seconds is about 133.3 million bits per second. Allow more for overhead; with 20% overhead you would need about 167 Mbps.
How much bandwidth does my website need?
Multiply monthly page views by the average page size. 100,000 views of 2 MB pages is 200 GB a month, an average of about 608 kbps. A redundancy factor, such as 1.5, adds a margin for busy periods: 300 GB a month and about 913 kbps.